Symptomatological analyses on clinically definite multiple sclerosis(MS) in Hokkaido disclosed two subgroups, one presenting acute transverse myelopathy(ATM) during the course of illness ("Japanese type MS"): and the other "Western type MS" without ATM. The latter form was found to be more prevalent than the former in this island. MRI studies showed less frequent lesions in cerebral white matter and brainstem in "Japanese type MS".In order to investigate racial factors, 43 consecutive clinically definite MS patients in Hokkaido was evaluated for HLA profiles. HLA-DRw8 was significantly increased, while DR9 was significantly decreased in these cases, being different from the association with DR2 in MS in Western countries. In analyzing HLA haplotypes in more details, so-called "Japanese type MS" has some association with HLA-DRQ7, while "Western type MS" with DR4 andDRw8.The incidents of oligoclonal IgG band in CSF of Japanese MS are said to be quite low, comparing with MS in Western countries. To evaluate these, collaborative studies on CSF analyses are underway between MS clinic, UBC, Canada and our department.Recently, anticardiolipin antibody positive cases were found among clinically definite MS presenting optic neuritis and transverse myelitis. These cases should be differentiated from MS in future. Hokkaido, the northernmost island of Japan, has quite similar climate, land, way of living to other cold, northern region countries, being different from the rest of Japan. The importance of clinical and epidemiological studies in this island should be stressed.